Declaring variables after statements.

I have seen this done in some code samples and seen Salem saying that its not allowed in standard C. What I was wondering is when is memory allocated and what the lifespan of the variable is when it is declared after statements.

example:

Code:

int foo (void)
{
int blah, blah2;
blah = something;
switch (blah)
          {
          case 1:
                  blah2+=1;
                  break;
         case 2:
                 int blah3;
                 blah3=blah * blah;
                 break;
         case 3:
                 blah2=ok;
                 break;
        }
return 0;
}

Could blah3 be used in case 3? case 1?

I personally dont like it but I'd like to know how it works none the less.

In C you can't define variables after any statements. You can only do that in C++. You will get a compiler error in compiling that code.
Depending on the version of the C++ compiler, earlier versions of compilers will have the scope of blah3 to be until the end of the function. Later versions, i think would have the scope end at the end of the switch statement.

In other words, your code is illegal because blah3 is not defined at a block beginning. This will work, though:

Code:

int foo (void)
{
int blah, blah2;
blah = something;
switch (blah)
          {
          case 1:
                  blah2+=1;
                  break;
         case 2:
              {
                 int blah3;
                 blah3=blah * blah;
                 break;
              }
         case 3:
                 blah2=ok;
                 break;
        }
return 0;
}

In this case, blah3 is only available within the block defined.

Sorry to necro this post, but another thread brought this topic to my attention...

I was under the impression that you cannot declare variables after any statements in a function. However this code compiles and executes...

Code:

#include <stdio.h>

int main()
{
	int input;
	int x,y,z,zZ;

	scanf("%d", &input);

	x=y=input;
	
	int table[x][y];
	int testVar = 0;

	for (z=0; z < input ; z++)
	{
		for (zZ = 0; zZ < input ; zZ++ )
		{
			table[z][zZ] = zZ;
		}
	}
	for (z=0; z < input ; z++)
	{
		for (zZ = 0; zZ < input ; zZ++ )
		{
			printf("%d",table[z][zZ] = zZ);
		}
		printf("\n");
	}
	printf ("%d\n",testVar);

	return 0;
}

Originally Posted by Scribbler

Sorry to necro this post, but another thread brought this topic to my attention...

I was under the impression that you cannot declare variables after any statements in a function. However this code compiles and executes...

(Holy OLD THREAD, Batman!)

That's because you can declare variables whenever you feel like it...

...in C99. Linky.

Quzah.